The present National Fire Protection Association (NFPA) standard governing minimum requirements for design and installation of automatic fire sprinkler systems is the 1999 Edition of NFPA 13 entitled “Standard for the Installation of Sprinkler Systems,” the complete disclosure of which is incorporated herein by reference. According to the National Fire Protection Association, NFPA 13 was first issued in 1896 under direction of the NFPA Committee on Automatic Sprinklers. The standard is periodically revised and updated as new information and technology become available.
The 1999 Edition of NFPA 13 recognizes various classes of occupancies, termed: “Light Hazard,” “Ordinary Hazard,” “Extra Hazard,” and “Special Occupancy Hazard,” as well as various types of storage commodity classes, including: “Miscellaneous Storage” and “High-Piled Storage,” the latter being categorized as including solid-piled, palletized, rack storage, bin box, and shelf storage in excess of twelve feet in height. NFPA 13 specifies the various levels of protection requirements for automatic fire sprinkler systems in these different types of occupancies, based, e.g., on severity of the potential fire hazard.
As generally defined by NFPA 13, Light Hazard occupancies are those where the quantity and/or combustibility of contents are low and fires with relatively low rates of heat release are expected. Ordinary Hazard covers those occupancies where the quantity and/or combustibility of the contents is equal to or greater than that of Light Hazard, ranging from low to high, where the quantity of combustibles is moderate and stock piles do not exceed twelve feet, such that fires with moderate to high rates of heat release are expected. Extra Hazard occupancies are those where quantity and combustibility of the contents are very high, and flammable or combustible liquids, dust, lint or other materials are present, such that the probability of rapidly developing fires with high rates of heat release is very high.
NFPA 13 does not specifically define Miscellaneous Storage and High-Piled Storage occupancies in terms of quantity and combustibility of material contents. Rather, it specifies various levels of fire protection requirements based on the type (combustibility) of materials (e.g., metal, paper, wood, plastics, rubber, etc.), amount of material, height of storage, and clearance between the top of the storage and the ceiling, as well as how the materials are stored (e.g., palletized, rack storage, solid-piled, etc.) and the method of packaging (e.g., cartoned, uncartoned, encapsulated, etc.).
NFPA 13 specifies maximum areas of protection per sprinkler for the various hazard occupancies. For example, in the case of a hydraulically calculated standard spray upright or pendent sprinkler system, the maximum protection area per sprinkler is: 225 square feet for a Light Hazard application with unobstructed ceiling construction; 130 square feet for an Ordinary Hazard application with all types of approved ceiling construction; and 100 square feet for Extra Hazard and High-Piled Storage applications with a water discharge density requirement equal to or greater than 0.25 gallon per minute per square foot, for any type of approved ceiling construction. The maximum area of protection per sprinkler for Miscellaneous Storage is determined by its Ordinary Hazard or Extra Hazard classification. This invention is specifically directed to protection of at least Extra Hazard and High-Piled Storage occupancies.
NFPA 13 also defines the protection area of a sprinkler as being at least rectangular (it may be square) and equal to:S×L 
where: S represents the greater of the distance from the sprinkler in question to the farthest spaced, immediately adjoining sprinkler, upstream or downstream, on the same supply line, or twice the distance from the sprinkler in question to a wall where the sprinkler in question is the last sprinkler on a supply line extending in a direction towards the wall, and L represents the greater of the perpendicular distance to the farthest spaced branch line immediately adjoining either lateral side of the branch line supporting the sprinkler in question, or twice the perpendicular distance to the farthest spaced wall immediately adjoining either side of the branch line which supports the sprinkler in question and which lacks an immediately adjoining branch line between it and the wall.
For example, in the case of a hydraulically calculated standard spray upright or pendent sprinkler system, the maximum spacing between sprinklers is: 15 feet for a Light Hazard application with unobstructed ceiling construction and for an Ordinary Hazard application with all types of approved ceiling construction; and 12 feet for Extra Hazard and High-Piled Storage applications with the water discharge requirement being equal to or greater than 0.25 gallon per minute per square foot.
A standard spray sprinkler, in either an upright or pendent deflector configuration, discharges a hemispherical-like pattern below the sprinkler deflector. Standard spray sprinklers are defined by Underwriters Laboratories Inc. (“UL”) as having a nominal K Factor in the range from 1.4 to 11.2 where:Q=K√P 
where: P represents the pressure of water fed into the inlet end of the internal passageway through the body of the sprinkler, in pounds per square inch gauge (psig); Q represents the flow of water from the outlet end of the internal passageway through the body of the sprinkler, in gallons per minute (gpm); and K represents the nominal K-factor constant in units of gallons per minute divided by the square root of pressure expressed in psig.
The maximum allowable spacing and minimum water discharge requirements for standard spray upright and pendent sprinklers are prescribed by NFPA 13 based on fire tests suitable to the selected hazard performed on like type sprinklers. Consequently, Listing agencies such as Underwriters Laboratories Inc. evaluate standard spray upright and pendent sprinklers to a set series of sprinkler performance tests at established spacing and water discharge values, to validate that the sprinklers will be suitable for use in applications prescribed in NFPA 13.
By comparison, extended coverage sprinklers, which are considered by NFPA 13 to be a type of Special Sprinkler and intended for the protection of areas greater than those for standard spray sprinklers, for an equivalent hazard, must be evaluated in a series of fire tests related to the intended hazard, at maximum sprinkler spacing and minimum water discharge requirements specified by the manufacturer. These fire tests established by the Listing agency (e.g., UL) are in addition to whatever water distribution, thermo-sensitivity, mechanical property, and environmental resistance tests are deemed appropriate, and which would also be applied to standard spray upright and pendent sprinklers.
In 1973, Section 4-1.1.1.3 was adopted and incorporated into NFPA 13, stating: “Special sprinklers may be installed with larger protection areas or distance between sprinklers than are specified in sections 4-2 and 4-5 when installed in accordance with the approvals or listing of a testing laboratory.” At the time, Sections 4-2 and 4-5 defined the maximum spacing and protection areas indicated above, for standard spray sprinklers.
In 1987 that section of NFPA 13 was amended to read: “Special sprinklers-installation of special sprinklers with protection areas, locations and distances between sprinklers differing from those specified . . . shall be permitted when found suitable for such use based on fire tests related to hazard category, tests to evaluate distribution, wetting of floors and walls, and interference to distribution by structural elements and tests to characterize response to sensitivity.”
Underwriters Laboratories, Inc. is the independent laboratory most widely utilized in the United States for testing and listing of fire protection sprinklers and it was the first to list Special Sprinklers. The main UL sprinkler test standard for sprinklers conforming to NFPA 13 is UL 199, entitled “Standard for Automatic Sprinklers for Fire-Protection Service.”
Prior to the inventions described in Meyer et al. U.S. Pat. No. 5,366,022, issued Nov. 22, 1994, and the inventions described in subsequent related patents, including: Meyer et al. U.S. Pat. No. 5,579,846, issued Dec. 3, 1996; Meyer et al. U.S. Pat. No. 5,584,344, issued Dec. 17, 1996; Meyer et al. U.S. Pat. No. 5,609,211, issued Mar. 11, 1997; and Meyer et al. U.S. Pat. No. 5,644,630, issued Sep. 9, 1997; UL had only listed extended coverage types of Special Sprinklers for use in Light Hazard applications. Commercial embodiments of the above patents to Meyer et al. were extended coverage sprinklers with nominal K-factors of 11.2 and 14.0 for use in Ordinary Hazard applications.
The listing of upright and pendent, extended coverage type Special Sprinklers for use in Extra Hazard and High-Piled Storage applications was permitted under provisions of the 1973 through 1994 Editions of NFPA 13, although these editions of NFPA 13 did not include any installation guidance requirements specific to use of extended coverage type Special Sprinklers in Extra Hazard and High-Piled Storage applications. In anticipation of future expansion of Listings in these categories, in the 1996 Edition of NFPA 13, the NFPA incorporated maximum protection area and maximum spacing criteria for extended coverage upright and pendent spray sprinklers, as a function of ceiling construction type. Although the 1996 Edition of NFPA 13 did not provide performance requirements specific to the concept of extended coverage upright and pendent spray sprinklers for Extra Hazard and High-Piled Storage applications, it did specify maximum protection area of 196 square feet and maximum spacing of 14 feet for these applications. This was a reduction from the 400 square feet maximum protection area and 20 foot maximum spacing criteria previously applied to any type Special Sprinkler, due to concern that, in Extra Hazard and High-Piled Storage applications, a larger protection area and spacing might overtax adjacent sprinklers, should one sprinkler not operate as anticipated.
In preparation for the NFPA Annual Meeting held on May 20-23, 1996, during which time the 1996 Edition of NFPA 13 was acted upon, the NFPA issued a “Report on Comments.” The “Report on Comments,” which members were asked to bring to the Annual Meeting, was a compilation of NFPA Technical Committee Reports or Comments provided for review by the NFPA membership prior to consideration at the meeting. The “Report on Comments” included description of action taken by the Committee on Automatic Sprinklers on a proposal by Mr. Peter Thomas of The Viking Corporation concerning the table on Sprinkler Discharge Characteristics Identification (Table 2-2.2 in 1996 Edition, changed to Table 3-2.3.1 in the 1999 Edition of NFPA 13). Mr. Thomas proposed that reference to a nominal 17 K-factor sprinkler should not be included in the Table, since it was not required for use with either standard or extended coverage sprinkler spacing, and that nominal 22 K-factor and 30 K-factor sprinklers would be preferred for extended coverage Extra Hazard and, possibly, for High-Piled Storage occupancies. However, the Thomas proposal did not consider, or reference, thermal sensitivity characteristics of the heat-responsive trigger of nominal 22 K-factor or 30 K-factor sprinklers, which would be essential to determining suitability of sprinklers for use as extended coverage upright and pendent spray sprinklers protecting Extra Hazard and High-Piled Storage occupancies in accordance with the 1999 Edition of NFPA 13.
Although guidelines for installation of extended coverage upright and pendent spray sprinklers in Extra Hazard and High-Piled Storage occupancies were included in the 1996 Edition of NFPA 13, prior to the present invention, neither Underwriters Laboratories Inc. (UL) Standard UL199, entitled “Standard for Automatic Sprinklers for Fire-Protection Service,” nor Factory Mutual Research Corporation (FM) Standard Class Series 2000, entitled “Approval Standard for Automatic Sprinklers for Fire Protection,” contained any reference to listing and/or approval requirements for use of extended coverage upright and pendent spray sprinklers in Extra Hazard and High-Piled Storage occupancies, even though both documents contained explicit listing and/or approval test requirements for use of extended coverage upright and pendent spray sprinklers in Light Hazard and Ordinary Hazard occupancies.
Furthermore, Meyer et al. U.S. Pat. No. 5,366,022, and the subsequent related patents listed above, suggested that the heat-responsive trigger in extended coverage sprinklers for use in Light Hazard and Ordinary Hazard occupancies should provide the quickest possible response times, in order to activate the sprinkler as soon as possible after the beginning of a fire. Meyer et al. further suggested that the response time index (RTI) of the heat-responsive trigger should be less than 100 meter1/2sec1/2 (m1/2s1/2) and preferably less than 50 meter1/2sec1/2 (m1/2s1/2). Also, the Meyer et al. patents teach that sprinklers with a K-factor greater than 8.7 are preferred for extended coverage sprinklers for use in Light Hazard and Ordinary Hazard occupancies, in order to minimize the water pressure required at the inlet end of the internal passageway through the body of the sprinkler, and thereby to reduce possible need for a booster pump in the sprinkler system water supply to establish adequate pressure for water fed into the inlet ends of the sprinklers.